Automatic telephone system.



B. G. DUNHAM.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED JAN. 31. l9l6.

Patented Apr. 3, 1917.

2 SHEETS-SHEET l li/QMMW: W DMMMW B. G. DUNHAM.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED JAN.3I. 1916.

Patented Apr. 3,1917.

2 SHEETS-SHEET 2.

kuxbm m sides in the provision of to Keith and Erickson,

BERT G. JD'UNHAM, OF HAWTHORNE, NEW

3 ASSIGNOR TO WESTERN ELECTRIC COMPANY, DECORPOBATED, OF NEW YORK,

N. '35., A CORPORATION OF NEW YORK.

AUTOMATIC TELEPHONE SYSTEM.

Specification of Letters Patent.

Application filed January 81, 1916. Serial No. 75,337.

To all whom it may concern:

Be it known that I, BERT G. DUNI-IAM, a citizen of the United States, residing at Hawthorne, in the county of Passaic and State of New Jersey, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to automatic telephone systems of the type in which but two wires (the talking conductors) are multipled through the several switches used in establishing a talklng connection. A system of this general character, is disclosed in application of Charles L. Goodrum, Serial No. 35,326, filed June 21, 1915.

One of the features of this invention rea system of the above described character, in which the release of the connector switch is controlled by the stepping relay prior to the response of the called'subscriber, and subsequent to such response, is controlled solely by the called subscriber.

Anotherfeature of the invention resides in the peculiar arrangement of the ringing control circuits.

Other features sult from or are incident above noted, will appear as of the invention which re- .to the features the description .of the invention progresses.

In the drawings, Figures 1 and 2 with Fig. 1 at the left shows the circuits of the invention and diagrammatically indicates the apparatus employed therewith. Any step-by-step two movement switch may be employed with the circuit shown. A switch of this general character is shown-in patent No. 815,176. Each a circuit changing device for controlling certain operating circuits thereat. These devices may be of the general character of the switch shown in the above mentioned patent and referred to therein as a side switch, but a circuit controlling device, such as shown in an applicaswitch is provided with tion of Oscar F. Forsberg, Serial No. 6302,

filed Feb'.-"5, 1915, will preferably be employed. Such a circuit controlling device may be caused to efiect circuit changes either upon the energization or upon 7 zation of its operating or escape 'magnet.

Each line of the exchange is provided with a line relay 1 and a cut-off relay 2 and Fig. 2.

the deenergr.

when desired, with a message register magnet 3, which are individual thereto. The lines of the exchange are arranged in groups of ten each, and for each group of ten lines the circuit controlling apparatus shown in the dotted rectangle at the lower left-hand corner of Fig. 1, is provided. The test relay 4, in addition to being common to any of the ten lines of its group, may be used to control any of the group of line finder switches which have access tov these lines.

The switches employed in the present system Wlll preferably be hundred point switches, the contacts being arranged in ten groups of ten contacts in a group.

As the vcircuits of the present invention are simple in character, it is thought the invention will be readily understood from the description .of the establishment and the dis establishment of a connection.

We will assume that the subscriber at the station shown at the left in Fig. 1 desires to establish a talking connection to the subscribers station appearing at the right in Upon the calling subscriber removing his receiver from the hook, a circuit is completed from battery through the left winding of line relay 1, back contact and lower armature of cut-off relay 2, over the left side of the subscribers line through the substation apparatus thereat, back over the right side of the line through the upper armature and back contact of relay 2 and the right Winding of relay 1 back to battery. Relay 1 is energized and completes a circuit from battery through relay 5, contact and left armature of relay 6, to ground through the left armature of relay 1. Relay 5 is energized and locks up through its left armature. The group test contact 7 of the calling line is connected to ground through the outermost right armature of relay 5. The

inner right armature of relay 5 completes a circuit from battery through the rotary stepping magnet 8, its, individual interrupter 9,

wiper 10, armature and contact of release I magnet 11, relay 6, inner right armature and front contact of relay 5 to ground throughthe armature of relay 1. The brushes 12 and 13 of the line finder switch are stepped from group to group of the terminals of the lines terminating therein.

When the group test brush 14; engages the test contact 7, individual to the group of the calling line, a circuit is completed from battery through the escape magnet 15, wiper-16,

line of thegroup of the calling subscriber,

When the test brush 12 engages the contact of the calling line, a circult is completed from a source of current through test relay 4, contact and right armature of relay 1 through the rightwinding of register magnet 3, brush 12,-side switch wiper 18, condenser 20 to ground through the resistance 21. Test relay 4 receives animpulse of current over thiscircuit, which causes it to attract its armature and interrupt the circuit of the vertical stepping magnet. In position 2 of the side switch, a circuit for the escape magnet 15 was maintamed from battery through escape magnet 15, wiper 16, contact and armature of magnet ll, relay 6, armature and front contact of relay 5 to ground through the armature of the test relay 4. The attraction of the armature .of the test relay also interrupts this circuit and the escape magnet 15 is denergized, thus moving the side switch to position 3.

A circuit is now established from battery through the left winding of magnet 3, cutoff relay 2, brush 13, wiper 22 to ground through resistance 21. Relay 2 is energized but magnet 3 is not operated. The attraction of the armatures of relay 2 interrupts the circuit for the line relay 1, which falls 011 and in turn interrupts the circuit for relay 5. The starter wire 23, which was interrupted at the back contact and innermost right armature of relay 5 is now completed, and as the side switch is now in position 3, this starter wire is now extended through wiper 10 to the portion of the starter circuit 23' leading to the next switch.

It may be here noted that the register magnet 3 is of such a character that current through either one of its windings will not serve toattract its armature, but it will be operated only when the current. through both windings is in such a direction as assist each other.

When the side switch moved to position 3, a circuit was completed to battery through resistance 24, wiper 25, line relay 26, wiper 19, brush 12 right wmding of magnet 3,

inner contact and upper armature of relay 2 over the subscribers line through the substation thereof and back through the lower armature and front contact of relay 2, brush 13, wiper 22 and resistance 21 to ground.

Relay 26 will-be energized over this circuit,

. but as thecurrent therein is of a polarity to oppose the action of the current through the left winding of magnet 3, the register magnet will not attract its armature; Relay 26 completes a circuit from battery through escape magnet 27, armature and contact of release magnet 28, wiper 29, contact and armature of rotary stepping magnet 30, rdtary elf-normal contact 31, front contact and armature of relay 26 to ground. The escape magnet is energized but does not move the side switch wipers.

The calling subscriber now operates his dial to send the first series of impulses, which in the system here disclosed, will be the thousands series. The sending device may be of any known construction which causes a seriesof momentary interruptions in the line circuit. With each interruption at the sending device, the previously traced circuit for relay 26 will be interrupted,causing it to retract its armature, thus completing a circui't from battery through rotary magnet 30, wiper 32, front contact and armature of escape magnet 27 and back contact and armature of relay 26 to ground. As the magnet 30 is repeatedly energized and deenergized over this circuit, the brushes 33 and 34 of the first selector switch will be stepped from group to group of the'trunks terminating thereat. With the first rotary step the rotary off-normal switch 31 opens its upper contact and closes its lower contact, and throughout the remaining impulses of the series the escape magnet 27, which is slow to release, is held up through the lower rotary off-normal contact 31 and the back contact and armature of relay 26.

Upon the termination of the series of impulses the relay 26 remains energized, thus holding open the circuit for magnet 27 which retracts its armature and moves the side switch to position 2. A circuit is now completed from battery through the vertical magnet 35, its individual interrupter 36, wiper 37, back contact and right armature of test relay 38 and front contact and armature of relay 26 to ground.

The selector switch brushes are now stepped from trunk "to trunk in the group of trunks selected. When the brush 33 engages the terminal of an idle trunk, a circuit is completed from battery through relay 38, brush 33, lower contact of rotary'olfnormal switch 39, back contact and arma ture of escape magnet 40, back contact a a:

' position mamas moves the side switch to position 3. A circuit is now completed from battery through line relay 41, brush 34, wiper 46, wiper 46, impedance coil 47 and front contact and armature of relay 26 to ground. Relay 41 completes a circult from battery through the escape magnet 40, armature and contact of release magnet armature of stepping rotary magnet 44, upper contact of rotary ofi-normal switch 45, and front contact and armature of relay 41 to ground. Escape magnet is energized over the circuit, but does not move the side switch wiper.

The calling subscriber now operates his dial to send the next or hundreds series of impulses. With each denergization of the relay 26, the circuit just traced through relay 41 is interrupted, and in retracting its armature it completes a circuit from battery through rotary magnet 44, wiper 48, front contact and armature of escape magnet 40 and back contact and armature of relay 41 to ground. The brushes 49 and 50 of the second selector are thus stepped from group to group of the trunks terminating in connector switches. Upon the first rotary impulse, switch 45 leaves its upper contact and engages its lower contact, and throughout the remaining impulses of the series the escape magnet 40, being slow to release, is maintained energized at the back contact of relay 41. At the termination of the series of impulses, relay 41 remains energized and thus holds open the circuit for escape magnet 40, which retracts its armature and moves the side switch to position 2.

A circuit is now completed from battery through the vertical stepping magnet 51, its individual interrupter 52, wiper 53, back contact and armature of test relay 54 to ground through the front contact and armature of relay 41. The switch brushes are thus stepped from trunk to trunk until the terminals of a trunk leading to an idle connector switch are found, when a circuit is completed from battery through test relay 54, brush 49, lower contact of rotary ofi-normal switch 55 contact and left amature of relay 56, back contact and armature of line relay 57 and the normal contact of release magnet 58 to ground. Relay 54 in attracting its armature, interrupts the circuit for the vertical stepping magnet and completes a circuit from battery through escape magnet 40, armature and contact of release magnet 42, wiper 43, front contact and armature of relay 54 to ground through the front'contact and armature of relay 41. Magnet 40 is energized and moves the side switch to In position 3 a circuit is completed from battery through line relay 57 brush 50, wiper 60, brush 34, wiper 46, impedance 47 and front contact and armature of line re- 42, wiper 43, contact and lay 26 to ground. Relay 57 pulls up and completes a circuit from battery through relay 56, wiper 61, contact and armature of rotary magnet 62, lower contact of rotary cit-normal switch 63 and front contact and armature of relay 57 to ground through a normal contact of release magnet 58. Re-

lay 56 completes a circuit through escape a magnet 64, front contact and right armature of relay 56, contact and armature of trip magnet 65, wiper 66 to thev lower talking conductor and thence to ground through relay 67. Escape magnet 64 is energized but does-not move the side switch.

The calling subscriber now operates the dial to send the tens series of impulses. With each interruption of the line circuit relay 26 retracts its armature and interrupts the circuit for relay 57 which in falling off completes a circuit from battery through rotary magnet 62, wiper 68, front contact and left armature of relay 56, back contact and armature of relay 57 to ground through the normal contact of release magnet 58. lVith the first rotary step, spring 63 opens at its lower contact and closes at its upper contact, and throughout the remaining impulses of the series, relay 56 is maintained energized through a circuit extending from the back contact of relay 57. At the end of the series relay 57 remains energized, thus holding open the circuit for relay 56, which in retracting its armature opens a circuit for the escape magnet 64, causing the side switch to move to position 2.

The subscriber now sends the unit series of impulses, repeatedly energizing and deenergizing relay 57 as before. When the side switch went to position 2, a circuit was completed from battery through relay 56, wiper 61, contact and armature of vertical step-v the previously traced circuit for the escape magnet 64, which is energized, but as before does not'move the side switch upon its energization. With each deenergization of the line relay 57, a circuit is now completed from battery through vertical stepping magnet 69, wiper 68, front contact and left armature of relay 56, back contact and armature of relay 57 to ground through the normal contact of magnet 58. The unit series of impulses causes the connector switch brushes 71 and 72 to be stepped from line to line of the group of the called subscriber. On the first vertical impulse, the spring 70 opened at its lower contact and closed at its upper contact and throughout the remainder of the series of impulses the relay 56 is I right armature and contact will retract its armature and of the series ofimpulses, the relay 56. retracts its armature and opens the circuit for the escape magnet 64 as before.

The escape magnet being slow to release, holds up its armature until the test of the called line has taken place. The retraction of the right armature of relay 56 opens the circuit of relay 67, which retracts its armature and completes a circuit from battery through the right winding of test relay-73, of relay 67, wiper 74 and brush72 to the test contact of the wanted line. If the wanted subscribers line is busy as a callingline, the test contact will be connected to ground through the resistance 21 of the trunk line connected there- 'to, and if it is busy as 2. called line, the test terminal will be connected to ground through brush 72, wiper 74 and relay 67 of the connector switch associated therewith.

Assuming now that the wanted line is idle, its test contact will be connected only through the cut-off relay 2 and consequently the test relay energized, and thus the escape and battery, will not be magnet 64 remove the side switch to position 3. In position 3 a clrcuit is completed from battery through cut-01f relay 2 of the called line, brush 72, 30.

wiper 74 and its third contact, right armature and contact of test relay 73 and relay 67 to ground. Relays 2 and 67 will both be energized. Relay 2' will'cut o the line relay of the called line. Relay 67 completes a circuit from a source of ringing current through ringing trip relay 65, left armature and contact of relay 67, wiper 75, brush 71, over the left side of the subscribers line through the bell at the substation thereof,

. back over the right side of the line to ground through relays 2 and 67 in parallel. When the side switch moved to position 3, a circuit was completed from escape magnet 64, front contact and right armature of relay 56, back contact and armature of relay 65, wiper 66 to ground through .the back contact and armature of relay 76; the escape magnet was energized but did not move the side switch. When the'called subscriber responds, an increased flow of current through trip magnet causes it to attract its armature and interrupt the circuit for the escape magnet just traced, thus causing the side switch to move to position 4. This opens the ringing circuit at side switch wiper 75, it also connects the upper talking conductor to ground through lead 77, side switch wiper 78 and the left winding of test relay 73. It is immaterial whether or not the test relay is operated over this circuit'at this time, as the lead from both of its armatures is now open at the side switch. Grounding the upper talking conductor completes a circuit for test relay 38 at the first selector, which, in attracting its armature, interrupts the to battery circuit which previously extended from battery through the escape magnet 27, armature back contact and right armature o relay 38 to ground through the front contact and armature of relay 26. Thus the escape magnet will become deenergized and move the first selector side switch to position 4. It will be noted that the fourth contact engaged by the wiper 25, is connectedto battery of opposite polarity to the battery associated with the first contacts of this wiper. Now with the side switch in position 4, a circuit extends from battery through wiper 25, relay 26, wiper 19, brush 12, right winding of register upper armature of cut-ofi relay 2 over the right side of the subscribers line, back over the left side of the line through the lower armature and front contact of relay 2, brush the called subscriber through relays 76 and 67.

The release of the finder switch and the first and second selector switches is controlled by the calling subscriber and the release of the connector switch is controlled by the called subscriber.

Assuming that upon the termination of the conversation the called subscriber is first to replace his receiver on the hook, then the circuit for relay 76 will be interrupted, causing it to interrupt the circuit for relay 56. This circuit extends through wiper 61, (position 4), and the front contact and armature of relay 76. Relay 56 falls ofi and completes a circuit from'battery through release magnet 58, rotary off-normal spring 55 and its upper contact, back contact and left armature of relay 56, wiper 66, in position 4, armature and back contact of relay 65 to ground through the right armature and back contact of relay 56. Release magnet 58 is energized and locks up through its armature and alternate contact, thus returning the connector switch to normal.

When the calling subscriber replaces his receiver on the hook, line relay 26 is deenergized and interrupts the circuit for the escape magnet 27 extending through the armature and contact of release magnet 28, wiper 29 (position 4), and front contact and armature of relay 26. Escape magnet 27 retracts its armature and completes a circuit from battery through the release magnet 11 of the finder switch and the release magnet mama 28 of the first selectorswit chin parallel,

magnets 11 and 28 are energized and restore the line finder and the first selector switches to normal. The release magnet 11 upon energization, opens up the starter circuit; the retraction of the armature of relay-26 also causes the denergization of line relay 41 of the second selector, relay 41 opens the circuit for the escape magnet 40, which extended through the armature and contact of release magnet 42, wiper 43 (position 3), and the front contact and armature of relay 41. Magnet 40 retracts its armature and completes a circuit from battery through release magnet 42, rotary off-normal spring 39 and its upper contact, back contact and armature of magnet 40, back contact and armature of relay 41 to ground, thus causing the release and return to normal of the second selector. All of the apparatus used in establishing the connection has now been returned to normal position.

We will now assume that the wanted subscribers line is busy. As before explained the lower terminal or test contact of the wanted line will now be connected to ground; therefore, when the relay 67 retracts its armature at the end of the units series of impulses, while the side switch is still in position 2, an energizing circuit will be completed from battery through right winding of test relay 73, right armature and back contact of relay 67, wiper 74;, brush 72 to the test terminal of the line and thence to ground through a relay 67 or through a resistance 21 depending upon whether the line is busy as a called or a calling line. The escape ma et 64: now retracts its armature and the side switch goes to position 3, where a circuit is completed from battery through the coil of thebusy-tone apparatus 81, left armature and front contacts of test relay 73 wiper 78 and through the left winding of relay 7.3 to ground, thus maintaining the relay energized. The busy-tone device 81 will now be connected to the upper talking strand .through the left armature of relay 73 and side switch wiper 82. In position 3 an energizing circuit is completed from battery through relay 56, wi er 61, front contact and armature of relay 5 to ground through the normal contact of release magnet 58. The relay 56 will pull up and complete the previously traced circuitfor escape magnet 64: through wiper 66 and back contact and armature of relay 76; thus the side switch will be maintained in position 3, busy-tone will be connected to the talking conductor until the calling subscriber replaces his receiver on the hook, when the restoration to normal of the finder switch and the first and second selector switches will occur in exactly the same manner as hereinbefore described. The release of the connector switch, however, is now controlled by the calling subscriber, and when the line relay 57 retracts its armature, a circuit is completed from battery through release magnet 58, rotary oil-normal spring 55 and its upper contact, contact and left armature of relay 56, back contact and armature of relay 57 to ground through the normal contact of relay 58. Release magnet 58 pulls up and locks through its armature and alternate contact, thus restoring the connector switch to normal.

Should the calling subscriber replace his receiver on the hook while a series of impulses are being transmitted, the escape magnet and the switch stepping magnet will both be held up or maintained energized by circuits extending through the back contacts of the line relays, were it not for the fact that the circuit for the escape magnet at each switch is carried through aback contact and armature of the stepping magnet or magnets, which are controlled by the impulses from the substation sending device. Considering first the first selector, it will be seen that if the subscriber should hang up while the series of impulses were being transmitted, relay 26 would retract its armature and thus maintain the circuit for the rotary magnet 30 closed. It will be remembered that the escape magnet 27, after the first rotary step, was maintained energized by a circuit extending through the back contact of relay 26, but as this circuit for the escape magnet 27 passes through the back contact and armature of the rotary magnet 30, the circuit for the escape magnet will be held open and it will retract its armature, completing a circuit from battery through the release magnets 11 and 28 in parallel, rotary off-normal contact 80, back contact'and armature of the escape magnet to ground through the back contact and armature of the line relay26.

As practically the same operation will occur at the second selector an at the connector switch, if the subscriber hun up while the impulses were being transmltted, the release of these switches will be readily understood and therefore will not be further described.

Should the calling subscriber only momentarily remove his receiver from the hook, it would start the line finder switch, but the relay 6 would immediately retract its armature and a circuit would be completedfrom battery through release magnet 11, rotary off normal contact 83, back contact and right armature of relay 6, back contact and left armature of escape magnet 27 to ground through the back contact and armature of line relay 26, thus causing the return to normal of the finder switch.

' -What is claimed is:

1. In a telephone system, a connector switch, a brush arranged to be included in the talking circuit at said switch, a test relay for said switch, means for joining said test relay to said brush, a ringing relay and a circuit for said ringing relay extendin through said brush, and a contact of sai test relay. 4

2. In a telephone system, a connector switch, a pair of brushes arranged to be included in the talking circuit at said switch, a test relay for said switch, means for joining said test relay to one of said brushes, a ringing relay, a circuit for said ringing relay extending through said brush, and a back contact of said test relay, a source of able contact for said switch both arranged I to be included in the talking circuit switch a test relay for said switch, means for join ing said test relay to said movable contact, a ringing relay permanently" connected to said conductor and a circuit for said ringing relay extending through said brush, and a contact of said test relay. V

In witness whereof, .I hereunto subscribe my name this 27th day of January, A. D'. 1916.

BERT G. DUNHAM. 

